Personal watercraft generally include a water propulsion device which is powered by an internal combustion engine. These watercraft are generally quite small in size, often limited to use by a single person.
The engine of the watercraft is positioned in an enclosed engine compartment defined by a hull of the watercraft. Due to the small size of the watercraft, the engine compartment is very small, and thus the engine is arranged in fairly compact fashion therein.
When of the two-cycle variety, the engine generally has fuel delivered to incoming air for combustion via one or more carburetors. The carburetor provides a relatively simple mechanism for providing fuel (i.e. it does not require complex electronic controls which may be associated with a fuel injection system) and is relatively reliable.
In many applications, the use of a carburetor having a single fuel supplying mechanism and throttle valve is sufficient. The nature of a watercraft makes it very desirable, however, to provide a mechanism for adding a large quantity of fuel over and above the basic fuel supplying mechanism. In particular, when moving a watercraft from a trolling or stopped position to its planing position, watercraft acceleration is required. For the engine to provide the necessary acceleration, a great deal of fuel must be supplied to the engine. This amount of fuel, however, is much larger than that generally required when the engine is idling or when running at a relatively steady high speed, such as after the watercraft has planed.
As such, the carburetor may be provided with a fuel increasing mechanism or "accelerating pump" arranged to supply a large amount of fuel in certain situations. Often, this mechanism includes a fuel chamber in which a cache of fuel is stored until the necessary delivery time.
A problem exists that this fuel cache is often a fuel chamber which is located at the engine and which is subject to the very high heat generated by the engine and trapped in the small engine compartment. The exposure of the fuel cache to these high temperatures contributes to evaporation of the fuel. Since the time between period of engine acceleration may be quite high, when the need for the supply of extra fuel arises, the fuel chamber may be empty or at least depleted.
An improved accelerating pump arrangement for an engine powering a watercraft is desired.